Mid-infrared supercontinuum generation in a dual-core photonic crystal fiber based on lead-bismuth-gallate glass

Supercontinuum (SC) generation with broad spectral coverage in the near-infrared (IR) and mid-IR ranges is critical for applications such as medical diagnostics, biomedical sensing, and optical coherence tomography. In this study, we demonstrate SC generation in a 10 cm lead-bismuth-gallate dual-core photonic crystal fiber (DC-PCF), where the structural symmetry ensures that the dispersion curves of all four supermode components are nearly identical. Using the generalized nonlinear Schrödinger equation (GNSE), we analyze how pump wavelength, peak power, and pulse width influence the resulting SC spectra. Pumping at 1560 nm, within the normal dispersion regime, and with a peak power of 30 kW, produces a broadband SC spanning 1275.8-2475.8 nm (1200 nm bandwidth) at 30 dB. In contrast, pumping in the anomalous dispersion regime at 1950 nm with the same peak power yields an SC bandwidth of 2353 nm at 30 dB. This bandwidth increase, compared to those of a single-core PCF under identical conditions, results from enhanced nonlinear mixing and inter-core energy transfer, which are facilitated by the intermodal interference of the supermode components in the DC-PCF. The proposed DC-PCF can be fabricated using conventional stack-and-draw techniques, making it a promising candidate for the development of coherent SC light sources.